1. Field of the Invention
The present invention relates to a carbon thin body having a unique structure, a process for producing the same, and an electric field emission type electron source using the same; and in particular to a carbon thin body which is expected to be used as an electron generating source in a display device, a process for producing the same, and an electric field emission type electron source using the same.
2. Description of the Background Art
Hitherto, as a unique structure of a carbon thin body, for example, carbon nanotubes have been known. As shown in FIG. 25, the carbon nanotubes are made in the form that carbon tubes 113 whose tips are closed are perpendicularly extended from a substrate 102. At the beginning when the carbon nanotubes were discovered, the carbon nanotubes were not formed for a particular purpose and no method of using the nanotubes was ascertained. However, by arranging the nanotubes in a planar form, it has become possible to obtain a compact and high-performance planar electric field emission type electron source. As, in the planar electric field emission type electron source, its tip portions are sharper, a more intense electric field for pulling electrons to the vicinity of the tip portions is easily built. As an index representing the efficiency of electron-emission for the electric field, an electric field amplification factor is used. It is also necessary to heighten the density of the sharp tips which are electron emitting points. The emission current, which is an index of performance of an electric field emission type electron source, is in proportion to the product of the electric field amplification factor, the density of the electron emitting points and the area of the electron source. The emission current can be precisely evaluated by simulation using the diameter W of carbon nanotubes and the interval d between the carbon nanotubes in a model of perpendicularly-oriented carbon nanotubes, as shown in FIG. 26.
The use of the carbon body made of the carbon nanotubes as a planar electron source has been expanded. Because of its unique structure, however, it has been considered that the carbon nanotube has no known use.
However, (a) carbon nanotubes are not formed unless the temperature of the substrate for them is raised to a given temperature or higher; (b) an expensive catalyst is required for forming nanotubes; (c) carbon nanotubes have small adhesion to the substrate owing to their structure; and (d) in the case that carbon nanotubes are used as a planar electron source, it is necessary to use a conductive substrate, or form the carbon nanotubes after a conductive film is formed on a nonconductive substrate since the respective nanotubes are electrically independent of each other. As shown in FIG. 27, in order to supply an electric current or voltage to perpendicularly-oriented carbon nanotubes 113 when the substrate 102 is insulating, it is necessary to deposit a conductive film 105 on the substrate 102 and then form the perpendicularly-oriented carbon nanotubes thereon. The electric current or voltage is supplied from an electric current source or a voltage source to the conductive 105.
In the case that carbon nanotubes are used as a planar electron source, an inexpensive glass substrate cannot be used because of the substrate temperature referred to in item (a). This hinders the use of carbon nanotubes, which are originally expensive The drawbacks referred to in items (b) and (d), together with the drawback referred to in item (a), cause an increase in costs for making carbon nanotubes for a planar electron source.